Regulator for electric motors



e. H. WHITTINGHAM.

REGULATOR FOR ELECTRIC'MOTORS.

APPLICATION FILED rum. I912. asnawso mm. 26. 1920.

1,340,679. Patented May 18, 1920.

UNITED STATES manna omen ononen nwnrr'rmem, or emission rhnx, MARYLAND, assrenon TO nom'ron com'nonnnn comrm-or nan'rmona, or nanrmoaa, nanrnmn, a conrona- TION' OF IABYLAND.

naeunaron ron nnno'rme morons.

Specification of Letters Patent.

Patented May 1s, 19%.

Applicationfled February 1, 1917, Serial No. 146,008. Renewed larch 26, 1920i Serial No. 369,028.

7 I To all whom it may concern.-

A i v I switches,

'the following a specification.

Be it known that I, Gao'nor. H. Wm'nrino- HAM, a citizen of the United States, residing at Bancroft Park, in the county of Baltimore and State of Maryland, have invented certain new and useful Improvements in Regulators for Electric Motors, ofwhmh This invention relates to controllin circuit for weakening and strengthening the field to vary. the speed of the motor.

The invention comprises a regulating member for adjusting the amount of. resistance in the shunt .fieldicircuit, a normall closed relay switch connecting said mem r in the field circuit, a normally open relay switch arranged in a .circuitshunting the resistance,'and means, common to said .and controlled. by the armature current,"for vibrating the normally closed switch when the regulating. member is moved to decreasethe resistance in the field circuit, and for vibrating the normally open switch when said member is'moved to increase the resistance in the field circuit. It is desirable to be able to set the hand regulating .member for any desired'running speed with out causing an excessive amount of current to flow in the armature circuit, and this is accomplished by means of the vibrating switcheswhich operate, upon change in the position of the regulatin -member,'to rapidly throw in an out t e field resistance until the motor adjusts itself to the running speed pre-determined by the adjustment of the regulating member. In the accompanying drawing, which illustrates my invention, diagrammatically, the two sides of the supply circuit are indicated at l and 2, the motor armature is indicated at 3, and the shunt field of the motor is indicated at 4. The shunt field circuit is indicated at 5, extending from the supply wire 1, through field resistance 5to the field winding 4, and thence to the supply wire 2. The armature circuit 6, of the motor, ex-

tends fromithe supply circuit 1, through a .to the armature 3 and the supply wire 2. The device 0 comprises the iron armature 9,

surrounded by a polarizing coil 10, the wind means for electric-motors havingshunt fiel wind'-' construction, an excess current in the arma-. ture circu t in one direction will cause the core or armature 9 to move endwise, in one direction, and an excess armature current in the opposite direction will cause the core to move oppositely. Opposite theends of the core 9 are arranged switch arms 12 and 13,

so thatwhen the core is moved in one direction it will move the switch arm 12, and

' when .the core is moved in the opposite direction it will move the switch arm 13. The switch arm 12 normally rests against a contact 14, the arm and contact constituting a switch '8, which is normally held closed by a spring 15. The switch arm 13 is normally held against a stop 16, by the spring 15, and when the switch arm 13 is moved away from the sto it engages a-contact 17. The arm 13 an contact 17 constitute a normally open switch 8.

The switch a normally. connects a hand regulating arm or member 18 with the field. wire 5 by conductors 19 and 20, the arrangement being such that when the re ulating member is on the last contact 210 the resistance, the latter will be entirely shortcircuited, and as said ember is moved to the left the amount oi iesistance short-circuited will be decreased until, when the member 18 rests on the contact 22, all of the field resistance -will be included in circuit with the field windings. The switch arms 12 and 13 are shown connected to- I the switch 8' is closed, the field resistance 5 is short-circuited through conductor 19, switch 8, conductor 23, switch s, and conductor 24.

In operation, assuming the line switch to be closed and the regulating member 18 to be resting upon the contact 21 of the resistance, the resistance will be entirely out out, the circuit flowin through the shunt around the resistance ormed by conductor 19, switch 8, conductor 20 and member 18. Thus, the motor will operate at normal speed with full field strength. If, now, the member 18 is ,moved from the contact 21 to its position shown in the drawing, on contact 25, that part of the resistance between contacts and 21 will be included in the field circuit, and this will cause the field to be weakened and the armature current will increase corresponding The increase in the armature current w1l cause the coil 8 to move the polarized core 9 against'the switch arm 13 and the switch 8 W111 be closed, thus momentarily short-circuit sistance, causing the I eld to strengthen and the armature current to fall. Because of the decrease in the armature current the polarized core 9 is drawnback by the coil 10 and the switch '8 is allowed to open, which again results in the int'rdd'uction of the resistance included between contacts 21' and 25. The closure and o ning of the switch a will be 1 continued rapidly, alternately including and excluding the field resistance while the motor armature is increasing its speed to that re-determinedby the position of the regulating memberlB. Any further movement of the regulating arm 18 to increase the resistance in the field circuit will be followed by vibration of the switch 8' while the motor is adjusting itself to its higher pro-determined speed. On the other hand; if the member 18 is moved in a direction to cut resistance out of the field circuit, for the purpose of slowing down the motor, the switch a will be vibrated until the motor comes to its lower pre-se't speed, when the vibration will stop. Thus, if the member 18 is. on the contact 22, wherein all the field resistance is incircuit, and said member is then moved to contact 25, or the contact 21,

cutting out a part or all of the resistance, the field of the motor will be suddenly strengthened and the armature, owin to its inertia, and while slowing down, wil gene-p rate a'current in the circuit 6 in the reverse direction, which will cause the polarized .the entire field recore 9 to strike a inst the switch arm 12 and open the switc 0, thus interru ting the circuit throu h the member 18 an momentarily includmg the entire field resistance in the field circuit This will be immediately followed by a dro in the armature current and the closure 0 the switch 8, which will include the member 18 and cut out resistance, again weakening the field, with the result that the armature will again send a current in the reverse direction through the coil 8, and the core 9 will a in open the switch a. This vibration wil be continued until the armature reaches a speed in accordance' with the field strength determined by the osition of the member 18.

hat I claim is 1. The combination with an electric motor having a shunt field winding, of a resistance in the field circuit, a member for regulating the amount of resistance in said circuit, a normally closed relay switch for including said member in said circuit, a normally open relay switch for shunting said resistance, a polarized armature adapted to actuate either of said switches, and means for actuating said polarized armature comprisin a 0011 included in the armature circuit o the motor.

2. The combination with an electric motor having a shunt field winding, of a resistance in the field circuit, a member for regulating the amount of resistance in said circuit, a normally closed rela switch for including said member in said circuit, a normally open rela switch for shunting said resistance, a .po arized armature arranged between the movable members of said switches and adapted to actuate each member separately, and means for actuating the polarized armature comprising a coll included in the armature circuit.

In testimony whereof I have allixed my signature.

GEORGE H. WHITTINGHAM. 

